Apparatus for measuring strip thickness



Nov. 17, 1953 Patented Nov. 17, 1953 AIPPARATUS FOR MEASURING s'rm THICKNESS George H. Rendel, Pittsburgh, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Application February 15, 1952, Serial No. 271,687

Claims.

This invention relates to an apparatus for measuring the thickness of metal strip as it passes through a rolling mill.

Before strip is introduced to a roll stand, the spacing between the rolls is adjusted to a prev determined distance to furnish a rolled product of the desired thickness. However, the thickness of the rolled product is not the same as the initial roll spacing, but varies principally because or two other major factors, namely the pressure of the strip against therolls and the temperature increase that takes place in roll bodies during a rolling operation. The pressure stretches the mill housings, compresses the roll bearin and also deflects or bends the rolls, and consequently increases the roll spacing and the strip thickness. The increase in temperature expands the roll bodies and consequently diminishes the roll spacing and the strip thickness. To maintain the desired strip thickness it is necessary to adjust the r011 spacing to compensate for both the pressure and temperature factors.

An object of the present invention is to provide a unitary apparatus which continuously measures the actual spacing between rolls by taking into account the pressure and temperature factors, and thus furnishes a continuous indication of the true strip thickness.

A further object is to provide such an apparatus which is composed of known types of measuring, transmitting, receiving and indicating devices in a novel combination that furnishes the desired indication accurately and practically instantaneously.

The single figure of the drawing shows schematically a roll stand which is equipped with an apparatus embodying principles of the present invention. The roll stand includes a pair of housings l0, upper and lower roll bearings l2 and I; supported in each of said housings, and upper and lower work rolls l4 and l 5 rotatably mounted in said bearings. The housings carry positioning screws I6 which are connected with the upper roll bearings I2 for adjusting the spacing between the rolls in the usual way. The screws are operated by a motor 41 through the usual shafts and bevel gears l8. The figure also shows a section of metal strip S which passes between the rolls It and I5 and is reduced in thickness as indicated in somewhat exaggerated fashion.

For measuring the initial roll spacing, the apparatus of the present invention includes a motion transmitter I! which is connected to motor I! and driven thereby. Preferably the transmitter 18 is electrical and is of the Selsyn" type. It is electrically connected to a difierential "Se1syn receiver 20, which in turn is connected to a decimal thickness indicator 2| through differential gearing 22 and an output shaft 23. When motor I! is operated to adjust the positioning screws I6 and change the spacing between the rolls, the transmitter [9, receiver 20 and differential gearing 22 also operate to change the reading on the indicator 2|. This indicator is calibrated to show the exact roll spacing.

The mill carries devices 24 for measuring the factor of roll pressure. Convenient devices for this purpose are strain gauges which can be mounted on the roll housings for measuring the elongation or stretch, or else on the roll bearings for measuring the compression". The roll pressure also deflects or bends the rolls, but these three main effects of pressure remain in proportion. Consequently, with proper calibration of the indicator, measurement of only one effect furnishes a measurement of the entire separation of the rolls caused by roll pressure. The strain gauges are connected to a pressure indicator 25, which preferably is of the recording-controller type, such as a Leeds and Northrup Speedomax otentiometer, and can be calibrated to indicate pounds of pressure and the additional roll separation in inches caused thereby. Pressure indicator 25 is mechanically connected to an electrical motion transmitter 26, preferably of the "Selsyn type similar to transmitter [9. Transmitter 26 is electrically connected to the receiver 20, which automatically adds the increase in roll spacing caused by the pressure to the reading transmitted to the decimal thickness indicator 2 I.

For measuring the factor of temperature increase, a temperature measuring device 21, such as a thermocouple, is mounted in contact with one of the rolls It or ii and is electrically connected with a temperature indicator 28. The latter indicator preferably is similar to the indicator 25, except that it is calibrated to show the roll temperature and in decimal parts of an inch the roll expansion caused by temperature increase over the initial temperature. The indicator 28 is mechanically connected to a motion transmitter 29, preferably also of the Selsyn type similar to transmitters I9 and 26. The transmitter 29 is electrically connected to a receiver 30, which in turn is connected to the differentlal gearing 22 on the opposite side from the receiver 20. The differential thus automatically subtracts the diminlshment in roll spacing caused by the factor of temperature increase from the reading transmitted to the decimal thickness indicator.

To explain the operation of the apparatus more carefully, I shall follow through a hypothetical example. First motor I! is operated to move the positioning screws [6 to the adjustment where rolls l4 and I5 just touch and the spacing is nil. Assume the roll temperature as indicated by the thermocouple 21 and temperature indicator 28 is 100 F. The decimal thickness indicator 2| now is set to read zero under these conditions. Assume further that the desired thickness of rolled product is 0.150 inch and that a roll pressure of approximately 1,000,000 pounds is expected during the rolling operation. The approximate increase in roll spacing for any given pressure is known; assume that 1,000,000 pounds pressure produces an increase of 0.070 inch, which is distributed among 0.010 inch stretch in the housings, 0.040 inch compression in the bearings, and 0.020 deflection in the rolls. The motor I! next is operated to move the positioning screws to the adjustment where the initial spacing between the rolls is 0.080 inch, which is the difierence between the desired strip thickness and the expected increase in roll spacing from pressure. The transmitter l9, receiver 20, and difierential gearing 22 transmit this reading to the decimal thickness indicator 2|, which now shows a spacing of 0.080 inch.

Next the strip s is introduced to the rolls. A pressure of 1,000,000 pounds would indicate 0.070 inch on recorder 25. The transmitter 26, receiver 20, and differential gearing 22 transmit this reading to the thickness indicator 2 I, which now shows 0.150 inch. If the pressure is somewhat greater or less than 1,000,000 pounds, the reading varies accordingly and the motor I! can be operated to make the necessary correction in the roll spacing.

As rolling proceeds, the roll temperature gradually increases. Assume that it reaches 350 F. and expands each roll 0.020 inch in diameter. The actual roll spacing diminishes by this same amount. The temperature increase and the diminishment in the roll spacing are indicated on the indicator 28. Transmitter 29 and receiver 30 transmit this change to the difierential gearing 22, which automatically subtracts it from the reading on the thickness indicator 2|. The motor I! again can be operated to make the necessary correction in the spacing of the rolls.

From the foregoing description it is seen that the present invention affords an apparatus which accurately and continuously measures strip thickness and thus enables the roll spacing to be corrected quickly to compensate for pressure and temperature factors. The various components of the apparatus, such as the strain gauges, the

thermocouple, the indicators, the transmitters,

the receivers, and the differential gearing, are parts of standard manufacture and therefore are not shown in detail.

While I have shown and described only a single embodiment of the invention, it is apparent that modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

I claim:

1. The combination, with a roll stand which includes r011 housings, work rolls rotatably supported in said housings, and positioning means for adjusting the spacing between said rolls, of

an apparatus for measuring the actual spacing between said rolls during a rolling operation and thus measuring the thickness of the rolled product comprising indicator means connected with said positioning means for measuringthe initial spacing between said rolls before a rolling operation begins, indicator means connected with said roll stand for measuring the increase in spacing between said rolls caused by pressure during rolling, indicator means connected with said rolls for measuring the dirninishment in roll spacing caused by the increase in roll temperature during rolling, and means interconnecting the three said indicator means to correct continuously during a rolling operation the measurement indicated on the first such means for changes caused by pressure and temperature.

2. The combination, with a roll stand which includes roll housings. work rolls rotatably supported in said housings, and positioning means for adjusting the spacing between said rolls, of an apparatus for measuring the actual spacing between said rolls during a rolling operation and thus measuring the thickness of the rolled product comprising indicator means connected with said positioning means for measuring the initial spacing between said rolls before a rolling operation begins, indicator means connected with said housings for measuring the increase in spacing between said rolls caused by pressure during rolling, means connecting said second indicator means with said first indicator means for adding their measurements, indicator means connected with said rolls for measuring the diminishment in roll spacing caused by the increase in roll temperature during rolling, and means connecting said third indicator means with the first two for subtracting continuously during a rolling operation its measurement from the combined measurement of the first two.

3. The combination with a roll stand which includes roll housings, work rolls rotatably supported in said housings, and positioning means for adjusting the spacing between said rolls, of an apparatus for measuring the actual spacing between said rolls during a rolling operation and thus measuring the thickness of the rolled product comprising a first transmitter connected with said positioning means for transmitting a measurement of the initial spacing between said rolls before a rolling operation begins, means connected with said housings for measuring the increase in spacing between said rolls caused by pressure during rolling, a second transmitter connected with said last named measuring-means, a first receiver connected to both said transmitters for adding the measurements transmitted thereby, means connected with said rolls for measuring the diminishment in roll spacing caused by the increase in roll temperature duringrolling, a third transmitter connected with said last named measuring means, a second receiver connected with said third transmitter, a differential connected at opposite sides to said receivers, and an indicator connected to said difierential.

4. The combination with a roll stand which includes roll housings, work rolls rotatably supported in said housings, positioning screws for adjusting the spacing between said rolls, and drive mechanism for said positioning screws, of an apparatus for measuring the actual spacing between said rolls during a rolling operation and thus measuring the thickness of the rolled product comprising a first transmitter connected with said drive mechanism for transmitting a measurement of the initial spacing between said rolls before a rolling operation begins, a strain gauge connected with said housings for measuring the increase in spacing between said rolls caused by pressure during rolling, an indicator and a second transmitter connected with said strain gauge, a first receiver connected to both said transmitters for adding the measurements transmitted thereby, a thermocouple connected with said rolls for measuring the diminishment in roll spacing caused by the increase in roll temperature during rolling, an indicator and a third transmitter connected with said thermocouple, a second receiver connected with said third transmitter, a differential connected at opposite sides to said receivers and having an output shaft, and an indicator connected to said output shaft.

/ 5. The eombinationwith a roll stand which includes roll housings, work rolls rotatably supported in said housings, positioning screws for ad: lusting the spacing between said rolls, and drive mechanism for said positioning screws, of an aparatus for measuring the actual spacing between said rolls during a rolling operation and thus measuring the thickness of the rolled product comprising a first Selsyn transmitter connected with said drive mechanism for transmitting a measurement of the initial spacing between said rolls before a rolling operation begins, a

strain, gauge connected with said housings for measuring the increase in spacing between said rolls caused by pressure during rolling, an indicator and a second Selsyn transmitter connected with said strain gauge, a first Selsyn receiver electrically connected to both said transmitters for adding the measurements transmitted thereby, a thermocouple connected with said rolls for measuring the diminishment in roll spacing caused by the increase in roll temperature during rolling, an indicator and a third "Selsyn transmitter connected with said thermocouple; a second selsyn receiver electrically connected with said third transmitter, a differential gearing connected at opposite sides to said receivers and having an output shaft, and a decimal thickness indicator connected to said output shaft.

GEORGE H. RENDEL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,332,288 zeitlin Oct. 19, 1943 2,345,931 Gates Apr. 4, 1944 2,603,001 Fox et a1 July 15, 1952 OTHER REFERENCES Publication: Selsyns, General Electric Co., Schenectady, N. Y., pamphlet (REA-21176. (Rec'd. Feb. 16, 1939, copy in 33-20456.) 

